A fuel cell is a device that generates electricity by a chemical reaction. Among various fuel cells, solid oxide fuel cells use a hard, ceramic compound metal (e.g., calcium or zirconium) oxide as an electrolyte. Typically, in solid oxide fuel cells, an oxygen gas, such as O2, is reduced to oxygen ions (O2−) at the cathode, and a fuel gas, such as H2 gas, is oxidized with the oxygen ions to form water at the anode. Fuel cells are generally designed as stacks, whereby subassemblies, each including a cathode, an anode and a solid electrolyte between the cathode and the anode, are assembled in series by locating an electrical interconnect between the cathode of one subassembly and the anode of another.
Zirconia stabilized by 8 mol % yttria (YSZ), such as, for example, from Tosoh (Tosoh USA, Grove City, Ohio), or from Unitec Ceramics (Stafford, United Kingdom), or from Daiichi Kigenso Kagaku Kogyo (Osaka, Japan) is commonly used as the electrolyte of solid oxide fuel cells (SOFCs) as it has a high oxygen ion conductivity and is quite stable in both oxidant and fuel atmospheres. A preferred YSZ is TZ-8Y powder from Tosoh USA. However, its high sintering temperature (about 1377° C. for TZ-8Y) limits its application in some areas such as co-firing multiple layers in the cell level and/or multiple cells in the stack level.
Therefore, a new approach is needed to minimize or eliminate the above mentioned problems.